1. Technical Field
The present invention relates to an evaporative cooling tower. More specifically, the invention relates to an improvement to the cooling tower that protects exposed components from elements that may affect reliability and productivity.
2. Description of the Prior Art
Many large industrial processes and laboratories, such as manufacturing plants, convention centers, hospitals, military command centers, and the like, operate 24 hours a day, 7 days a week, every week of the year. In many cases, the economic security, the public health, the public welfare, and the national security of our nation are all dependant upon the continued operation of these facilities. Additionally, many commercial and industrial processes and power plants generate heat that must be removed. It is imperative that a stable atmospheric temperature be maintained within these facilities such that employees may comfortably complete their assigned tasks, regardless of the weather conditions outside of the facility.
Evaporation of water through cooling towers has proven itself to be an effective and generally energy efficient mechanism to cool water that has been heated by a commercial, or industrial process. FIG. 1 illustrates an example of a prior art cooling tower. The cooling tower (10) of FIG. 1 is comprised essentially of a cooling tower fan (15), an evaporative fill (20), a nozzle or hot pan for distributing water to be evaporated across the evaporative fill (25), an above grade sump (30), a below grade water pipe directing cooling water into the facility (35), a below grade water pipe directing warm water from the facility (40), a by-pass valve (50), a by-pass balancing valve (45), and a standpipe riser (55). In operation, warm water is pumped into the fill (20) through the nozzle (25) and is cooled within the fill (20) by evaporation accelerated by air flow generated by the cooling tower fan (15). The cooled water is then stored in the above grade sump (30) and later pumped into a work facility through a below grade water pipe (35) to be used as cooling water by the facility, a process, or equipment. The use of the cooled water by the facility, equipment, or process increases the temperature of the water. In order for the water to continue to cool the work facility, the process, or equipment the water temperature must be reduced and controlled within a specific range, i.e., not too hot, nor too cold. One method for reducing the water temperature within a controlled range of temperatures is to recycle warmed work facility water through the cooling tower. Accordingly, warmed water from the facility travels from within the facility through the below grade pipe (35) to the above grade by-pass valve (50). At the by-pass valve (50), the warm water is either returned to the above grade sump (30) through the by-pass balancing valve (45) or returned to the nozzles or hot pan (25) through the stand-pipe riser (55), depending on the current load or operating status of the cooling tower. In general, the bypass valve (50) is modulated by a motor to vary the proportion of flow up to the tower fill (30) or down to the above grade sump (30) depending on the current load or operating status of the cooling tower.
One drawback of the above prior art is a potential for the above grade elements to freeze during cold weather conditions. Except for below grade pipes (35) and (40), the remaining components in the prior art cooling tower are above grade, and as such are periodically exposed to freezing temperatures. This exposure, together with water, can create a build up of ice on the above-grade components. Both the build up of ice and ice breaking off the cooling tower and falling can cause injury or property damage to the cooling tower (10) and any surrounding property. Additionally, the expansion force of ice formed within the cooling tower has the potential to fracture the cooling tower's components (10). Any or all of these events can drastically disrupt the function of the cooling tower (10) and, more importantly, catastrophically affect the productivity levels of the work facility. As the operation of the facility becomes more critical, such as a hospital, power plant, or military installation, redundant, or standby cooling towers are installed. Freeze protection in the standby equipment may be required for weeks, until there is a need to operate the redundant cooling tower. As a result, many cooling towers require insulation or heating mechanisms to prevent such ice formation. These insulation or heating mechanisms represent an additional cost to the facility and are not completely efficient at preventing ice formation. Accordingly, there is a need for a cost efficient and more reliable solution to the problem created by exposure of cooling tower components to freezing temperatures.
Placing the sump below grade is one solution to prevent freezing of above-grade components. FIG. 2 is a prior art diagram (90) illustrating one such prior art example of this solution. As shown, a cooling tower apparatus (100) is provided with a cooling tower fill (110), a cooling tower fan (105), a nozzle or hot pan (115), an open ended pipe (120), a below grade sump (125), a supply water turbine pump (130), a below grade water pipe directing cooling water into the facility (135), a below grade water pipe directing warm water from the facility (150), a by-pass valve (155), a by-pass balancing valve (140), and a stand pipe riser (145). Much like the prior art illustrated in FIG. 1, in FIG. 2 warm water travels into the cooling tower fill (100), or into the cooling tower (100), through a nozzle or hot pan (115) and is cooled in the fill (110) by a cooling tower fan (105). In one embodiment, the warm water is fed to the cooling tower from a remote work facility. The cooled water travels below grade through the open ended pipe (120) and is stored in the below grade sump (125). The cooled water is then pumped into the work facility through the below grade pipe (135) by the supply water turbine pump (130) to alter the facility's internal temperature. Upon use within the facility, the warmed water then travels from within the facility through the second below grade pipe (150) to the above grade by-pass valve (155). At the by-pass valve (155), the warm water is either returned to the below grade sump (125) through a by-pass balancing valve (140) or returned to the nozzle (115) through the stand-pipe riser (145), depending on the current load or operating status of the cooling tower. In general, the bypass valve (155) is modulated by a motor to vary the proportion of flow up to the tower fill (110) or down to the below grade sump (125) depending on the current load or operating status of the cooling tower.
The beneficial effect of the prior art illustrated in FIG. 2 is that by placing the sump below grade, the sump is insulated from freezing and the protection of the water from freezing becomes passive due to the fact that it is below grade and covered. This increases efficiency because the sump is able to utilize natural insulation provided by the ground and no additional cost is required. Reliability is improved since the heating mechanisms required to prevent the sump water from freezing are eliminated. Additionally, a supply water turbine pump (60) provides a reliable and efficient pump for introducing cooled water into the work facility.
However, freeze protection risks remain with FIG. 2's prior art design where the warm water return piping (150) is exposed to external temperatures when it exits the ground to return to the cooling tower from the facility. The most susceptible components include the by-pass valve (155), the by-pass balancing valve (140) and the stand-pipe riser (145). These components are susceptible to freezing because water can be trapped within these pipes when the valves are rotated to either the normal setting, wherein the warm water returns to the nozzle (15), or in the by-pass setting, wherein the warm water is returned to the sump (125). Freezing of the water within these pipes can lead to freezing and even destruction of the cooling tower components. Although, the by-pass valve (155), the by-pass balancing valve (140) and the stand-pipe riser (145) may be insulated or heated to prevent such ice formation, these insulation or heating mechanisms represent an additional cost to the facility and are not completely efficient at preventing ice formation.
Certain facility processes increase in energy efficiency when the sump water is cooler. In summer, the atmospheric conditions such as temperature and humidity limit the lowest temperature that can be achieved, but in cold weather, the sump temperature can be lowered to just above freezing. This colder supply water dramatically reduces the energy needed to operate the facility. In some cases, the energy efficiency of the mechanical plant can be increased by 20% due to the colder sump water. However, one significant problem with lowering the sump water temperature is freezing. Accordingly, an evaporative cooling tower is needed that reduces complex components and excessive energy waste such that freeze protection of the cooling tower is increased, the cooling tower's reliability is increased and the work facility, process and equipment can reliably maintain an adequate work temperature, regardless of the external temperature.